// Copyright 2005, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//
// This file implements death tests.

#include "gtest/gtest-death-test.h"
#include "gtest/internal/gtest-port.h"
#include "gtest/internal/custom/gtest.h"

#if GTEST_HAS_DEATH_TEST

#if GTEST_OS_MAC
#include <crt_externs.h>
#endif // GTEST_OS_MAC

#include <errno.h>
#include <fcntl.h>
#include <limits.h>

#if GTEST_OS_LINUX
#include <signal.h>
#endif // GTEST_OS_LINUX

#include <stdarg.h>

#if GTEST_OS_WINDOWS
#include <windows.h>
#else
#include <sys/mman.h>
#include <sys/wait.h>
#endif // GTEST_OS_WINDOWS

#if GTEST_OS_QNX
#include <spawn.h>
#endif // GTEST_OS_QNX

#if GTEST_OS_FUCHSIA
#include <lib/fdio/io.h>
#include <lib/fdio/spawn.h>
#include <zircon/processargs.h>
#include <zircon/syscalls.h>
#include <zircon/syscalls/port.h>
#endif // GTEST_OS_FUCHSIA

#endif // GTEST_HAS_DEATH_TEST

#include "gtest/gtest-message.h"
#include "gtest/internal/gtest-string.h"
#include "src/gtest-internal-inl.h"

namespace testing {

// Constants.

// The default death test style.
//
// This is defined in internal/gtest-port.h as "fast", but can be overridden by
// a definition in internal/custom/gtest-port.h. The recommended value, which is
// used internally at Google, is "threadsafe".
static const char kDefaultDeathTestStyle[] = GTEST_DEFAULT_DEATH_TEST_STYLE;

GTEST_DEFINE_string_(
    death_test_style,
    internal::StringFromGTestEnv("death_test_style", kDefaultDeathTestStyle),
    "Indicates how to run a death test in a forked child process: "
    "\"threadsafe\" (child process re-executes the test binary "
    "from the beginning, running only the specific death test) or "
    "\"fast\" (child process runs the death test immediately "
    "after forking).");

GTEST_DEFINE_bool_(
    death_test_use_fork,
    internal::BoolFromGTestEnv("death_test_use_fork", false),
    "Instructs to use fork()/_exit() instead of clone() in death tests. "
    "Ignored and always uses fork() on POSIX systems where clone() is not "
    "implemented. Useful when running under valgrind or similar tools if "
    "those do not support clone(). Valgrind 3.3.1 will just fail if "
    "it sees an unsupported combination of clone() flags. "
    "It is not recommended to use this flag w/o valgrind though it will "
    "work in 99% of the cases. Once valgrind is fixed, this flag will "
    "most likely be removed.");

namespace internal {
GTEST_DEFINE_string_(
    internal_run_death_test, "",
    "Indicates the file, line number, temporal index of "
    "the single death test to run, and a file descriptor to "
    "which a success code may be sent, all separated by "
    "the '|' characters.  This flag is specified if and only if the current "
    "process is a sub-process launched for running a thread-safe "
    "death test.  FOR INTERNAL USE ONLY.");
} // namespace internal

#if GTEST_HAS_DEATH_TEST

namespace internal {

// Valid only for fast death tests. Indicates the code is running in the
// child process of a fast style death test.
#if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
static bool g_in_fast_death_test_child = false;
#endif

// Returns a Boolean value indicating whether the caller is currently
// executing in the context of the death test child process.  Tools such as
// Valgrind heap checkers may need this to modify their behavior in death
// tests.  IMPORTANT: This is an internal utility.  Using it may break the
// implementation of death tests.  User code MUST NOT use it.
bool InDeathTestChild()
{
#if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA

    // On Windows and Fuchsia, death tests are thread-safe regardless of the value
    // of the death_test_style flag.
    return !GTEST_FLAG(internal_run_death_test).empty();

#else

    if (GTEST_FLAG(death_test_style) == "threadsafe")
        return !GTEST_FLAG(internal_run_death_test).empty();
    else
        return g_in_fast_death_test_child;
#endif
}

} // namespace internal

// ExitedWithCode constructor.
ExitedWithCode::ExitedWithCode(int exit_code)
    : exit_code_(exit_code)
{
}

// ExitedWithCode function-call operator.
bool ExitedWithCode::operator()(int exit_status) const
{
#if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA

    return exit_status == exit_code_;

#else

    return WIFEXITED(exit_status) && WEXITSTATUS(exit_status) == exit_code_;

#endif // GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA
}

#if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
// KilledBySignal constructor.
KilledBySignal::KilledBySignal(int signum)
    : signum_(signum)
{
}

// KilledBySignal function-call operator.
bool KilledBySignal::operator()(int exit_status) const
{
#if defined(GTEST_KILLED_BY_SIGNAL_OVERRIDE_)
    {
        bool result;
        if (GTEST_KILLED_BY_SIGNAL_OVERRIDE_(signum_, exit_status, &result)) {
            return result;
        }
    }
#endif // defined(GTEST_KILLED_BY_SIGNAL_OVERRIDE_)
    return WIFSIGNALED(exit_status) && WTERMSIG(exit_status) == signum_;
}
#endif // !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA

namespace internal {

// Utilities needed for death tests.

// Generates a textual description of a given exit code, in the format
// specified by wait(2).
static std::string ExitSummary(int exit_code)
{
    Message m;

#if GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA

    m << "Exited with exit status " << exit_code;

#else

    if (WIFEXITED(exit_code)) {
        m << "Exited with exit status " << WEXITSTATUS(exit_code);
    } else if (WIFSIGNALED(exit_code)) {
        m << "Terminated by signal " << WTERMSIG(exit_code);
    }
#ifdef WCOREDUMP
    if (WCOREDUMP(exit_code)) {
        m << " (core dumped)";
    }
#endif
#endif // GTEST_OS_WINDOWS || GTEST_OS_FUCHSIA

    return m.GetString();
}

// Returns true if exit_status describes a process that was terminated
// by a signal, or exited normally with a nonzero exit code.
bool ExitedUnsuccessfully(int exit_status)
{
    return !ExitedWithCode(0)(exit_status);
}

#if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
// Generates a textual failure message when a death test finds more than
// one thread running, or cannot determine the number of threads, prior
// to executing the given statement.  It is the responsibility of the
// caller not to pass a thread_count of 1.
static std::string DeathTestThreadWarning(size_t thread_count)
{
    Message msg;
    msg << "Death tests use fork(), which is unsafe particularly"
        << " in a threaded context. For this test, " << GTEST_NAME_ << " ";
    if (thread_count == 0) {
        msg << "couldn't detect the number of threads.";
    } else {
        msg << "detected " << thread_count << " threads.";
    }
    msg << " See "
           "https://github.com/google/googletest/blob/master/googletest/docs/"
           "advanced.md#death-tests-and-threads"
        << " for more explanation and suggested solutions, especially if"
        << " this is the last message you see before your test times out.";
    return msg.GetString();
}
#endif // !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA

// Flag characters for reporting a death test that did not die.
static const char kDeathTestLived = 'L';
static const char kDeathTestReturned = 'R';
static const char kDeathTestThrew = 'T';
static const char kDeathTestInternalError = 'I';

#if GTEST_OS_FUCHSIA

// File descriptor used for the pipe in the child process.
static const int kFuchsiaReadPipeFd = 3;

#endif

// An enumeration describing all of the possible ways that a death test can
// conclude.  DIED means that the process died while executing the test
// code; LIVED means that process lived beyond the end of the test code;
// RETURNED means that the test statement attempted to execute a return
// statement, which is not allowed; THREW means that the test statement
// returned control by throwing an exception.  IN_PROGRESS means the test
// has not yet concluded.
// FIXME: Unify names and possibly values for
// AbortReason, DeathTestOutcome, and flag characters above.
enum DeathTestOutcome { IN_PROGRESS,
                        DIED,
                        LIVED,
                        RETURNED,
                        THREW };

// Routine for aborting the program which is safe to call from an
// exec-style death test child process, in which case the error
// message is propagated back to the parent process.  Otherwise, the
// message is simply printed to stderr.  In either case, the program
// then exits with status 1.
static void DeathTestAbort(const std::string &message)
{
    // On a POSIX system, this function may be called from a threadsafe-style
    // death test child process, which operates on a very small stack.  Use
    // the heap for any additional non-minuscule memory requirements.
    const InternalRunDeathTestFlag *const flag =
        GetUnitTestImpl()->internal_run_death_test_flag();
    if (flag != NULL) {
        FILE *parent = posix::FDOpen(flag->write_fd(), "w");
        fputc(kDeathTestInternalError, parent);
        fprintf(parent, "%s", message.c_str());
        fflush(parent);
        _exit(1);
    } else {
        fprintf(stderr, "%s", message.c_str());
        fflush(stderr);
        posix::Abort();
    }
}

// A replacement for CHECK that calls DeathTestAbort if the assertion
// fails.
#define GTEST_DEATH_TEST_CHECK_(expression) \
    do { \
        if (!::testing::internal::IsTrue(expression)) { \
            DeathTestAbort( \
                ::std::string("CHECK failed: File ") + __FILE__ + ", line " \
                + ::testing::internal::StreamableToString(__LINE__) + ": " \
                + #expression); \
        } \
    } while (::testing::internal::AlwaysFalse())

// This macro is similar to GTEST_DEATH_TEST_CHECK_, but it is meant for
// evaluating any system call that fulfills two conditions: it must return
// -1 on failure, and set errno to EINTR when it is interrupted and
// should be tried again.  The macro expands to a loop that repeatedly
// evaluates the expression as long as it evaluates to -1 and sets
// errno to EINTR.  If the expression evaluates to -1 but errno is
// something other than EINTR, DeathTestAbort is called.
#define GTEST_DEATH_TEST_CHECK_SYSCALL_(expression) \
    do { \
        int gtest_retval; \
        do { \
            gtest_retval = (expression); \
        } while (gtest_retval == -1 && errno == EINTR); \
        if (gtest_retval == -1) { \
            DeathTestAbort( \
                ::std::string("CHECK failed: File ") + __FILE__ + ", line " \
                + ::testing::internal::StreamableToString(__LINE__) + ": " \
                + #expression + " != -1"); \
        } \
    } while (::testing::internal::AlwaysFalse())

// Returns the message describing the last system error in errno.
std::string GetLastErrnoDescription()
{
    return errno == 0 ? "" : posix::StrError(errno);
}

// This is called from a death test parent process to read a failure
// message from the death test child process and log it with the FATAL
// severity. On Windows, the message is read from a pipe handle. On other
// platforms, it is read from a file descriptor.
static void FailFromInternalError(int fd)
{
    Message error;
    char buffer[256];
    int num_read;

    do {
        while ((num_read = posix::Read(fd, buffer, 255)) > 0) {
            buffer[num_read] = '\0';
            error << buffer;
        }
    } while (num_read == -1 && errno == EINTR);

    if (num_read == 0) {
        GTEST_LOG_(FATAL) << error.GetString();
    } else {
        const int last_error = errno;
        GTEST_LOG_(FATAL) << "Error while reading death test internal: "
                          << GetLastErrnoDescription() << " [" << last_error << "]";
    }
}

// Death test constructor.  Increments the running death test count
// for the current test.
DeathTest::DeathTest()
{
    TestInfo *const info = GetUnitTestImpl()->current_test_info();
    if (info == NULL) {
        DeathTestAbort("Cannot run a death test outside of a TEST or "
                       "TEST_F construct");
    }
}

// Creates and returns a death test by dispatching to the current
// death test factory.
bool DeathTest::Create(const char *statement, const RE *regex,
                       const char *file, int line, DeathTest **test)
{
    return GetUnitTestImpl()->death_test_factory()->Create(
        statement, regex, file, line, test);
}

const char *DeathTest::LastMessage()
{
    return last_death_test_message_.c_str();
}

void DeathTest::set_last_death_test_message(const std::string &message)
{
    last_death_test_message_ = message;
}

std::string DeathTest::last_death_test_message_;

// Provides cross platform implementation for some death functionality.
class DeathTestImpl : public DeathTest
{
protected:
    DeathTestImpl(const char *a_statement, const RE *a_regex)
        : statement_(a_statement)
        , regex_(a_regex)
        , spawned_(false)
        , status_(-1)
        , outcome_(IN_PROGRESS)
        , read_fd_(-1)
        , write_fd_(-1)
    {
    }

    // read_fd_ is expected to be closed and cleared by a derived class.
    ~DeathTestImpl() { GTEST_DEATH_TEST_CHECK_(read_fd_ == -1); }

    void Abort(AbortReason reason);
    virtual bool Passed(bool status_ok);

    const char *statement() const { return statement_; }
    const RE *regex() const { return regex_; }
    bool spawned() const { return spawned_; }
    void set_spawned(bool is_spawned) { spawned_ = is_spawned; }
    int status() const { return status_; }
    void set_status(int a_status) { status_ = a_status; }
    DeathTestOutcome outcome() const { return outcome_; }
    void set_outcome(DeathTestOutcome an_outcome) { outcome_ = an_outcome; }
    int read_fd() const { return read_fd_; }
    void set_read_fd(int fd) { read_fd_ = fd; }
    int write_fd() const { return write_fd_; }
    void set_write_fd(int fd) { write_fd_ = fd; }

    // Called in the parent process only. Reads the result code of the death
    // test child process via a pipe, interprets it to set the outcome_
    // member, and closes read_fd_.  Outputs diagnostics and terminates in
    // case of unexpected codes.
    void ReadAndInterpretStatusByte();

private:
    // The textual content of the code this object is testing.  This class
    // doesn't own this string and should not attempt to delete it.
    const char *const statement_;
    // The regular expression which test output must match.  DeathTestImpl
    // doesn't own this object and should not attempt to delete it.
    const RE *const regex_;
    // True if the death test child process has been successfully spawned.
    bool spawned_;
    // The exit status of the child process.
    int status_;
    // How the death test concluded.
    DeathTestOutcome outcome_;
    // Descriptor to the read end of the pipe to the child process.  It is
    // always -1 in the child process.  The child keeps its write end of the
    // pipe in write_fd_.
    int read_fd_;
    // Descriptor to the child's write end of the pipe to the parent process.
    // It is always -1 in the parent process.  The parent keeps its end of the
    // pipe in read_fd_.
    int write_fd_;
};

// Called in the parent process only. Reads the result code of the death
// test child process via a pipe, interprets it to set the outcome_
// member, and closes read_fd_.  Outputs diagnostics and terminates in
// case of unexpected codes.
void DeathTestImpl::ReadAndInterpretStatusByte()
{
    char flag;
    int bytes_read;

    // The read() here blocks until data is available (signifying the
    // failure of the death test) or until the pipe is closed (signifying
    // its success), so it's okay to call this in the parent before
    // the child process has exited.
    do {
        bytes_read = posix::Read(read_fd(), &flag, 1);
    } while (bytes_read == -1 && errno == EINTR);

    if (bytes_read == 0) {
        set_outcome(DIED);
    } else if (bytes_read == 1) {
        switch (flag) {
        case kDeathTestReturned:
            set_outcome(RETURNED);
            break;
        case kDeathTestThrew:
            set_outcome(THREW);
            break;
        case kDeathTestLived:
            set_outcome(LIVED);
            break;
        case kDeathTestInternalError:
            FailFromInternalError(read_fd()); // Does not return.
            break;
        default:
            GTEST_LOG_(FATAL) << "Death test child process reported "
                              << "unexpected status byte ("
                              << static_cast<unsigned int>(flag) << ")";
        }
    } else {
        GTEST_LOG_(FATAL) << "Read from death test child process failed: "
                          << GetLastErrnoDescription();
    }
    GTEST_DEATH_TEST_CHECK_SYSCALL_(posix::Close(read_fd()));
    set_read_fd(-1);
}

// Signals that the death test code which should have exited, didn't.
// Should be called only in a death test child process.
// Writes a status byte to the child's status file descriptor, then
// calls _exit(1).
void DeathTestImpl::Abort(AbortReason reason)
{
    // The parent process considers the death test to be a failure if
    // it finds any data in our pipe.  So, here we write a single flag byte
    // to the pipe, then exit.
    const char status_ch =
        reason == TEST_DID_NOT_DIE ? kDeathTestLived : reason == TEST_THREW_EXCEPTION ? kDeathTestThrew : kDeathTestReturned;

    GTEST_DEATH_TEST_CHECK_SYSCALL_(posix::Write(write_fd(), &status_ch, 1));
    // We are leaking the descriptor here because on some platforms (i.e.,
    // when built as Windows DLL), destructors of global objects will still
    // run after calling _exit(). On such systems, write_fd_ will be
    // indirectly closed from the destructor of UnitTestImpl, causing double
    // close if it is also closed here. On debug configurations, double close
    // may assert. As there are no in-process buffers to flush here, we are
    // relying on the OS to close the descriptor after the process terminates
    // when the destructors are not run.
    _exit(1); // Exits w/o any normal exit hooks (we were supposed to crash)
}

// Returns an indented copy of stderr output for a death test.
// This makes distinguishing death test output lines from regular log lines
// much easier.
static ::std::string FormatDeathTestOutput(const ::std::string &output)
{
    ::std::string ret;
    for (size_t at = 0;;) {
        const size_t line_end = output.find('\n', at);
        ret += "[  DEATH   ] ";
        if (line_end == ::std::string::npos) {
            ret += output.substr(at);
            break;
        }
        ret += output.substr(at, line_end + 1 - at);
        at = line_end + 1;
    }
    return ret;
}

// Assesses the success or failure of a death test, using both private
// members which have previously been set, and one argument:
//
// Private data members:
//   outcome:  An enumeration describing how the death test
//             concluded: DIED, LIVED, THREW, or RETURNED.  The death test
//             fails in the latter three cases.
//   status:   The exit status of the child process. On *nix, it is in the
//             in the format specified by wait(2). On Windows, this is the
//             value supplied to the ExitProcess() API or a numeric code
//             of the exception that terminated the program.
//   regex:    A regular expression object to be applied to
//             the test's captured standard error output; the death test
//             fails if it does not match.
//
// Argument:
//   status_ok: true if exit_status is acceptable in the context of
//              this particular death test, which fails if it is false
//
// Returns true iff all of the above conditions are met.  Otherwise, the
// first failing condition, in the order given above, is the one that is
// reported. Also sets the last death test message string.
bool DeathTestImpl::Passed(bool status_ok)
{
    if (!spawned())
        return false;

    const std::string error_message = GetCapturedStderr();

    bool success = false;
    Message buffer;

    buffer << "Death test: " << statement() << "\n";
    switch (outcome()) {
    case LIVED:
        buffer << "    Result: failed to die.\n"
               << " Error msg:\n"
               << FormatDeathTestOutput(error_message);
        break;
    case THREW:
        buffer << "    Result: threw an exception.\n"
               << " Error msg:\n"
               << FormatDeathTestOutput(error_message);
        break;
    case RETURNED:
        buffer << "    Result: illegal return in test statement.\n"
               << " Error msg:\n"
               << FormatDeathTestOutput(error_message);
        break;
    case DIED:
        if (status_ok) {
#if GTEST_USES_PCRE
            // PCRE regexes support embedded NULs.
            const bool matched = RE::PartialMatch(error_message, *regex());
#else
            const bool matched = RE::PartialMatch(error_message.c_str(), *regex());
#endif // GTEST_USES_PCRE
            if (matched) {
                success = true;
            } else {
                buffer << "    Result: died but not with expected error.\n"
                       << "  Expected: " << regex()->pattern() << "\n"
                       << "Actual msg:\n"
                       << FormatDeathTestOutput(error_message);
            }
        } else {
            buffer << "    Result: died but not with expected exit code:\n"
                   << "            " << ExitSummary(status()) << "\n"
                   << "Actual msg:\n"
                   << FormatDeathTestOutput(error_message);
        }
        break;
    case IN_PROGRESS:
    default:
        GTEST_LOG_(FATAL)
            << "DeathTest::Passed somehow called before conclusion of test";
    }

    DeathTest::set_last_death_test_message(buffer.GetString());
    return success;
}

#if GTEST_OS_WINDOWS
// WindowsDeathTest implements death tests on Windows. Due to the
// specifics of starting new processes on Windows, death tests there are
// always threadsafe, and Google Test considers the
// --gtest_death_test_style=fast setting to be equivalent to
// --gtest_death_test_style=threadsafe there.
//
// A few implementation notes:  Like the Linux version, the Windows
// implementation uses pipes for child-to-parent communication. But due to
// the specifics of pipes on Windows, some extra steps are required:
//
// 1. The parent creates a communication pipe and stores handles to both
//    ends of it.
// 2. The parent starts the child and provides it with the information
//    necessary to acquire the handle to the write end of the pipe.
// 3. The child acquires the write end of the pipe and signals the parent
//    using a Windows event.
// 4. Now the parent can release the write end of the pipe on its side. If
//    this is done before step 3, the object's reference count goes down to
//    0 and it is destroyed, preventing the child from acquiring it. The
//    parent now has to release it, or read operations on the read end of
//    the pipe will not return when the child terminates.
// 5. The parent reads child's output through the pipe (outcome code and
//    any possible error messages) from the pipe, and its stderr and then
//    determines whether to fail the test.
//
// Note: to distinguish Win32 API calls from the local method and function
// calls, the former are explicitly resolved in the global namespace.
//
class WindowsDeathTest : public DeathTestImpl
{
public:
    WindowsDeathTest(const char *a_statement,
                     const RE *a_regex,
                     const char *file,
                     int line)
        : DeathTestImpl(a_statement, a_regex)
        , file_(file)
        , line_(line)
    {
    }

    // All of these virtual functions are inherited from DeathTest.
    virtual int Wait();
    virtual TestRole AssumeRole();

private:
    // The name of the file in which the death test is located.
    const char *const file_;
    // The line number on which the death test is located.
    const int line_;
    // Handle to the write end of the pipe to the child process.
    AutoHandle write_handle_;
    // Child process handle.
    AutoHandle child_handle_;
    // Event the child process uses to signal the parent that it has
    // acquired the handle to the write end of the pipe. After seeing this
    // event the parent can release its own handles to make sure its
    // ReadFile() calls return when the child terminates.
    AutoHandle event_handle_;
};

// Waits for the child in a death test to exit, returning its exit
// status, or 0 if no child process exists.  As a side effect, sets the
// outcome data member.
int WindowsDeathTest::Wait()
{
    if (!spawned())
        return 0;

    // Wait until the child either signals that it has acquired the write end
    // of the pipe or it dies.
    const HANDLE wait_handles[2] = {child_handle_.Get(), event_handle_.Get()};
    switch (::WaitForMultipleObjects(2,
                                     wait_handles,
                                     FALSE, // Waits for any of the handles.
                                     INFINITE)) {
    case WAIT_OBJECT_0:
    case WAIT_OBJECT_0 + 1:
        break;
    default:
        GTEST_DEATH_TEST_CHECK_(false); // Should not get here.
    }

    // The child has acquired the write end of the pipe or exited.
    // We release the handle on our side and continue.
    write_handle_.Reset();
    event_handle_.Reset();

    ReadAndInterpretStatusByte();

    // Waits for the child process to exit if it haven't already. This
    // returns immediately if the child has already exited, regardless of
    // whether previous calls to WaitForMultipleObjects synchronized on this
    // handle or not.
    GTEST_DEATH_TEST_CHECK_(
        WAIT_OBJECT_0 == ::WaitForSingleObject(child_handle_.Get(), INFINITE));
    DWORD status_code;
    GTEST_DEATH_TEST_CHECK_(
        ::GetExitCodeProcess(child_handle_.Get(), &status_code) != FALSE);
    child_handle_.Reset();
    set_status(static_cast<int>(status_code));
    return status();
}

// The AssumeRole process for a Windows death test.  It creates a child
// process with the same executable as the current process to run the
// death test.  The child process is given the --gtest_filter and
// --gtest_internal_run_death_test flags such that it knows to run the
// current death test only.
DeathTest::TestRole WindowsDeathTest::AssumeRole()
{
    const UnitTestImpl *const impl = GetUnitTestImpl();
    const InternalRunDeathTestFlag *const flag =
        impl->internal_run_death_test_flag();
    const TestInfo *const info = impl->current_test_info();
    const int death_test_index = info->result()->death_test_count();

    if (flag != NULL) {
        // ParseInternalRunDeathTestFlag() has performed all the necessary
        // processing.
        set_write_fd(flag->write_fd());
        return EXECUTE_TEST;
    }

    // WindowsDeathTest uses an anonymous pipe to communicate results of
    // a death test.
    SECURITY_ATTRIBUTES handles_are_inheritable = {
        sizeof(SECURITY_ATTRIBUTES), NULL, TRUE};
    HANDLE read_handle, write_handle;
    GTEST_DEATH_TEST_CHECK_(
        ::CreatePipe(&read_handle, &write_handle, &handles_are_inheritable,
                     0) // Default buffer size.
        != FALSE);
    set_read_fd(::_open_osfhandle(reinterpret_cast<intptr_t>(read_handle),
                                  O_RDONLY));
    write_handle_.Reset(write_handle);
    event_handle_.Reset(::CreateEvent(
        &handles_are_inheritable,
        TRUE, // The event will automatically reset to non-signaled state.
        FALSE, // The initial state is non-signalled.
        NULL)); // The even is unnamed.
    GTEST_DEATH_TEST_CHECK_(event_handle_.Get() != NULL);
    const std::string filter_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kFilterFlag + "=" + info->test_case_name() + "." + info->name();
    const std::string internal_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag + "=" + file_ + "|" + StreamableToString(line_) + "|" + StreamableToString(death_test_index) + "|" + StreamableToString(static_cast<unsigned int>(::GetCurrentProcessId())) +
        // size_t has the same width as pointers on both 32-bit and 64-bit
        // Windows platforms.
        // See http://msdn.microsoft.com/en-us/library/tcxf1dw6.aspx.
        "|" + StreamableToString(reinterpret_cast<size_t>(write_handle)) + "|" + StreamableToString(reinterpret_cast<size_t>(event_handle_.Get()));

    char executable_path[_MAX_PATH + 1]; // NOLINT
    GTEST_DEATH_TEST_CHECK_(
        _MAX_PATH + 1 != ::GetModuleFileNameA(NULL, executable_path, _MAX_PATH));

    std::string command_line =
        std::string(::GetCommandLineA()) + " " + filter_flag + " \"" + internal_flag + "\"";

    DeathTest::set_last_death_test_message("");

    CaptureStderr();
    // Flush the log buffers since the log streams are shared with the child.
    FlushInfoLog();

    // The child process will share the standard handles with the parent.
    STARTUPINFOA startup_info;
    memset(&startup_info, 0, sizeof(STARTUPINFO));
    startup_info.dwFlags = STARTF_USESTDHANDLES;
    startup_info.hStdInput = ::GetStdHandle(STD_INPUT_HANDLE);
    startup_info.hStdOutput = ::GetStdHandle(STD_OUTPUT_HANDLE);
    startup_info.hStdError = ::GetStdHandle(STD_ERROR_HANDLE);

    PROCESS_INFORMATION process_info;
    GTEST_DEATH_TEST_CHECK_(::CreateProcessA(
                                executable_path,
                                const_cast<char *>(command_line.c_str()),
                                NULL, // Retuned process handle is not inheritable.
                                NULL, // Retuned thread handle is not inheritable.
                                TRUE, // Child inherits all inheritable handles (for write_handle_).
                                0x0, // Default creation flags.
                                NULL, // Inherit the parent's environment.
                                UnitTest::GetInstance()->original_working_dir(),
                                &startup_info,
                                &process_info)
                            != FALSE);
    child_handle_.Reset(process_info.hProcess);
    ::CloseHandle(process_info.hThread);
    set_spawned(true);
    return OVERSEE_TEST;
}

#elif GTEST_OS_FUCHSIA

class FuchsiaDeathTest : public DeathTestImpl
{
public:
    FuchsiaDeathTest(const char *a_statement,
                     const RE *a_regex,
                     const char *file,
                     int line)
        : DeathTestImpl(a_statement, a_regex)
        , file_(file)
        , line_(line)
    {
    }
    virtual ~FuchsiaDeathTest()
    {
        zx_status_t status = zx_handle_close(child_process_);
        GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
        status = zx_handle_close(port_);
        GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
    }

    // All of these virtual functions are inherited from DeathTest.
    virtual int Wait();
    virtual TestRole AssumeRole();

private:
    // The name of the file in which the death test is located.
    const char *const file_;
    // The line number on which the death test is located.
    const int line_;

    zx_handle_t child_process_ = ZX_HANDLE_INVALID;
    zx_handle_t port_ = ZX_HANDLE_INVALID;
};

// Utility class for accumulating command-line arguments.
class Arguments
{
public:
    Arguments()
    {
        args_.push_back(NULL);
    }

    ~Arguments()
    {
        for (std::vector<char *>::iterator i = args_.begin(); i != args_.end();
             ++i) {
            free(*i);
        }
    }
    void AddArgument(const char *argument)
    {
        args_.insert(args_.end() - 1, posix::StrDup(argument));
    }

    template<typename Str>
    void AddArguments(const ::std::vector<Str> &arguments)
    {
        for (typename ::std::vector<Str>::const_iterator i = arguments.begin();
             i != arguments.end();
             ++i) {
            args_.insert(args_.end() - 1, posix::StrDup(i->c_str()));
        }
    }
    char *const *Argv()
    {
        return &args_[0];
    }

    int size()
    {
        return args_.size() - 1;
    }

private:
    std::vector<char *> args_;
};

// Waits for the child in a death test to exit, returning its exit
// status, or 0 if no child process exists.  As a side effect, sets the
// outcome data member.
int FuchsiaDeathTest::Wait()
{
    if (!spawned())
        return 0;

    // Register to wait for the child process to terminate.
    zx_status_t status_zx;
    status_zx = zx_object_wait_async(child_process_,
                                     port_,
                                     0 /* key */,
                                     ZX_PROCESS_TERMINATED,
                                     ZX_WAIT_ASYNC_ONCE);
    GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);

    // Wait for it to terminate, or an exception to be received.
    zx_port_packet_t packet;
    status_zx = zx_port_wait(port_, ZX_TIME_INFINITE, &packet);
    GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);

    if (ZX_PKT_IS_EXCEPTION(packet.type)) {
        // Process encountered an exception. Kill it directly rather than letting
        // other handlers process the event.
        status_zx = zx_task_kill(child_process_);
        GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);

        // Now wait for |child_process_| to terminate.
        zx_signals_t signals = 0;
        status_zx = zx_object_wait_one(
            child_process_, ZX_PROCESS_TERMINATED, ZX_TIME_INFINITE, &signals);
        GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);
        GTEST_DEATH_TEST_CHECK_(signals & ZX_PROCESS_TERMINATED);
    } else {
        // Process terminated.
        GTEST_DEATH_TEST_CHECK_(ZX_PKT_IS_SIGNAL_ONE(packet.type));
        GTEST_DEATH_TEST_CHECK_(packet.signal.observed & ZX_PROCESS_TERMINATED);
    }

    ReadAndInterpretStatusByte();

    zx_info_process_t buffer;
    status_zx = zx_object_get_info(
        child_process_,
        ZX_INFO_PROCESS,
        &buffer,
        sizeof(buffer),
        nullptr,
        nullptr);
    GTEST_DEATH_TEST_CHECK_(status_zx == ZX_OK);

    GTEST_DEATH_TEST_CHECK_(buffer.exited);
    set_status(buffer.return_code);
    return status();
}

// The AssumeRole process for a Fuchsia death test.  It creates a child
// process with the same executable as the current process to run the
// death test.  The child process is given the --gtest_filter and
// --gtest_internal_run_death_test flags such that it knows to run the
// current death test only.
DeathTest::TestRole FuchsiaDeathTest::AssumeRole()
{
    const UnitTestImpl *const impl = GetUnitTestImpl();
    const InternalRunDeathTestFlag *const flag =
        impl->internal_run_death_test_flag();
    const TestInfo *const info = impl->current_test_info();
    const int death_test_index = info->result()->death_test_count();

    if (flag != NULL) {
        // ParseInternalRunDeathTestFlag() has performed all the necessary
        // processing.
        set_write_fd(kFuchsiaReadPipeFd);
        return EXECUTE_TEST;
    }

    CaptureStderr();
    // Flush the log buffers since the log streams are shared with the child.
    FlushInfoLog();

    // Build the child process command line.
    const std::string filter_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kFilterFlag + "="
        + info->test_case_name() + "." + info->name();
    const std::string internal_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag + "="
        + file_ + "|"
        + StreamableToString(line_) + "|"
        + StreamableToString(death_test_index);
    Arguments args;
    args.AddArguments(GetInjectableArgvs());
    args.AddArgument(filter_flag.c_str());
    args.AddArgument(internal_flag.c_str());

    // Build the pipe for communication with the child.
    zx_status_t status;
    zx_handle_t child_pipe_handle;
    uint32_t type;
    status = fdio_pipe_half(&child_pipe_handle, &type);
    GTEST_DEATH_TEST_CHECK_(status >= 0);
    set_read_fd(status);

    // Set the pipe handle for the child.
    fdio_spawn_action_t add_handle_action = {};
    add_handle_action.action = FDIO_SPAWN_ACTION_ADD_HANDLE;
    add_handle_action.h.id = PA_HND(type, kFuchsiaReadPipeFd);
    add_handle_action.h.handle = child_pipe_handle;

    // Spawn the child process.
    status = fdio_spawn_etc(ZX_HANDLE_INVALID, FDIO_SPAWN_CLONE_ALL,
                            args.Argv()[0], args.Argv(), nullptr, 1,
                            &add_handle_action, &child_process_, nullptr);
    GTEST_DEATH_TEST_CHECK_(status == ZX_OK);

    // Create an exception port and attach it to the |child_process_|, to allow
    // us to suppress the system default exception handler from firing.
    status = zx_port_create(0, &port_);
    GTEST_DEATH_TEST_CHECK_(status == ZX_OK);
    status = zx_task_bind_exception_port(
        child_process_, port_, 0 /* key */, 0 /*options */);
    GTEST_DEATH_TEST_CHECK_(status == ZX_OK);

    set_spawned(true);
    return OVERSEE_TEST;
}

#else // We are neither on Windows, nor on Fuchsia.

// ForkingDeathTest provides implementations for most of the abstract
// methods of the DeathTest interface.  Only the AssumeRole method is
// left undefined.
class ForkingDeathTest : public DeathTestImpl
{
public:
    ForkingDeathTest(const char *statement, const RE *regex);

    // All of these virtual functions are inherited from DeathTest.
    virtual int Wait();

protected:
    void set_child_pid(pid_t child_pid) { child_pid_ = child_pid; }

private:
    // PID of child process during death test; 0 in the child process itself.
    pid_t child_pid_;
};

// Constructs a ForkingDeathTest.
ForkingDeathTest::ForkingDeathTest(const char *a_statement, const RE *a_regex)
    : DeathTestImpl(a_statement, a_regex)
    , child_pid_(-1)
{
}

// Waits for the child in a death test to exit, returning its exit
// status, or 0 if no child process exists.  As a side effect, sets the
// outcome data member.
int ForkingDeathTest::Wait()
{
    if (!spawned())
        return 0;

    ReadAndInterpretStatusByte();

    int status_value;
    GTEST_DEATH_TEST_CHECK_SYSCALL_(waitpid(child_pid_, &status_value, 0));
    set_status(status_value);
    return status_value;
}

// A concrete death test class that forks, then immediately runs the test
// in the child process.
class NoExecDeathTest : public ForkingDeathTest
{
public:
    NoExecDeathTest(const char *a_statement, const RE *a_regex)
        : ForkingDeathTest(a_statement, a_regex)
    {
    }
    virtual TestRole AssumeRole();
};

// The AssumeRole process for a fork-and-run death test.  It implements a
// straightforward fork, with a simple pipe to transmit the status byte.
DeathTest::TestRole NoExecDeathTest::AssumeRole()
{
    const size_t thread_count = GetThreadCount();
    if (thread_count != 1) {
        GTEST_LOG_(WARNING) << DeathTestThreadWarning(thread_count);
    }

    int pipe_fd[2];
    GTEST_DEATH_TEST_CHECK_(pipe(pipe_fd) != -1);

    DeathTest::set_last_death_test_message("");
    CaptureStderr();
    // When we fork the process below, the log file buffers are copied, but the
    // file descriptors are shared.  We flush all log files here so that closing
    // the file descriptors in the child process doesn't throw off the
    // synchronization between descriptors and buffers in the parent process.
    // This is as close to the fork as possible to avoid a race condition in case
    // there are multiple threads running before the death test, and another
    // thread writes to the log file.
    FlushInfoLog();

    const pid_t child_pid = fork();
    GTEST_DEATH_TEST_CHECK_(child_pid != -1);
    set_child_pid(child_pid);
    if (child_pid == 0) {
        GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[0]));
        set_write_fd(pipe_fd[1]);
        // Redirects all logging to stderr in the child process to prevent
        // concurrent writes to the log files.  We capture stderr in the parent
        // process and append the child process' output to a log.
        LogToStderr();
        // Event forwarding to the listeners of event listener API mush be shut
        // down in death test subprocesses.
        GetUnitTestImpl()->listeners()->SuppressEventForwarding();
        g_in_fast_death_test_child = true;
        return EXECUTE_TEST;
    } else {
        GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[1]));
        set_read_fd(pipe_fd[0]);
        set_spawned(true);
        return OVERSEE_TEST;
    }
}

// A concrete death test class that forks and re-executes the main
// program from the beginning, with command-line flags set that cause
// only this specific death test to be run.
class ExecDeathTest : public ForkingDeathTest
{
public:
    ExecDeathTest(const char *a_statement, const RE *a_regex,
                  const char *file, int line)
        : ForkingDeathTest(a_statement, a_regex)
        , file_(file)
        , line_(line)
    {
    }
    virtual TestRole AssumeRole();

private:
    static ::std::vector<std::string> GetArgvsForDeathTestChildProcess()
    {
        ::std::vector<std::string> args = GetInjectableArgvs();
#if defined(GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_)
        ::std::vector<std::string> extra_args =
            GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_();
        args.insert(args.end(), extra_args.begin(), extra_args.end());
#endif // defined(GTEST_EXTRA_DEATH_TEST_COMMAND_LINE_ARGS_)
        return args;
    }
    // The name of the file in which the death test is located.
    const char *const file_;
    // The line number on which the death test is located.
    const int line_;
};

// Utility class for accumulating command-line arguments.
class Arguments
{
public:
    Arguments()
    {
        args_.push_back(NULL);
    }

    ~Arguments()
    {
        for (std::vector<char *>::iterator i = args_.begin(); i != args_.end();
             ++i) {
            free(*i);
        }
    }
    void AddArgument(const char *argument)
    {
        args_.insert(args_.end() - 1, posix::StrDup(argument));
    }

    template<typename Str>
    void AddArguments(const ::std::vector<Str> &arguments)
    {
        for (typename ::std::vector<Str>::const_iterator i = arguments.begin();
             i != arguments.end();
             ++i) {
            args_.insert(args_.end() - 1, posix::StrDup(i->c_str()));
        }
    }
    char *const *Argv()
    {
        return &args_[0];
    }

private:
    std::vector<char *> args_;
};

// A struct that encompasses the arguments to the child process of a
// threadsafe-style death test process.
struct ExecDeathTestArgs {
    char *const *argv; // Command-line arguments for the child's call to exec
    int close_fd; // File descriptor to close; the read end of a pipe
};

#if GTEST_OS_MAC
inline char **GetEnviron()
{
    // When Google Test is built as a framework on MacOS X, the environ variable
    // is unavailable. Apple's documentation (man environ) recommends using
    // _NSGetEnviron() instead.
    return *_NSGetEnviron();
}
#else
// Some POSIX platforms expect you to declare environ. extern "C" makes
// it reside in the global namespace.
extern "C" char **environ;
inline char **GetEnviron()
{
    return environ;
}
#endif // GTEST_OS_MAC

#if !GTEST_OS_QNX
// The main function for a threadsafe-style death test child process.
// This function is called in a clone()-ed process and thus must avoid
// any potentially unsafe operations like malloc or libc functions.
static int ExecDeathTestChildMain(void *child_arg)
{
    ExecDeathTestArgs *const args = static_cast<ExecDeathTestArgs *>(child_arg);
    GTEST_DEATH_TEST_CHECK_SYSCALL_(close(args->close_fd));

    // We need to execute the test program in the same environment where
    // it was originally invoked.  Therefore we change to the original
    // working directory first.
    const char *const original_dir =
        UnitTest::GetInstance()->original_working_dir();
    // We can safely call chdir() as it's a direct system call.
    if (chdir(original_dir) != 0) {
        DeathTestAbort(std::string("chdir(\"") + original_dir + "\") failed: " + GetLastErrnoDescription());
        return EXIT_FAILURE;
    }

    // We can safely call execve() as it's a direct system call.  We
    // cannot use execvp() as it's a libc function and thus potentially
    // unsafe.  Since execve() doesn't search the PATH, the user must
    // invoke the test program via a valid path that contains at least
    // one path separator.
    execve(args->argv[0], args->argv, GetEnviron());
    DeathTestAbort(std::string("execve(") + args->argv[0] + ", ...) in " + original_dir + " failed: " + GetLastErrnoDescription());
    return EXIT_FAILURE;
}
#endif // !GTEST_OS_QNX

#if GTEST_HAS_CLONE
// Two utility routines that together determine the direction the stack
// grows.
// This could be accomplished more elegantly by a single recursive
// function, but we want to guard against the unlikely possibility of
// a smart compiler optimizing the recursion away.
//
// GTEST_NO_INLINE_ is required to prevent GCC 4.6 from inlining
// StackLowerThanAddress into StackGrowsDown, which then doesn't give
// correct answer.
static void StackLowerThanAddress(const void *ptr,
                                  bool *result) GTEST_NO_INLINE_;
static void StackLowerThanAddress(const void *ptr, bool *result)
{
    int dummy;
    *result = (&dummy < ptr);
}

// Make sure AddressSanitizer does not tamper with the stack here.
GTEST_ATTRIBUTE_NO_SANITIZE_ADDRESS_
static bool StackGrowsDown()
{
    int dummy;
    bool result;
    StackLowerThanAddress(&dummy, &result);
    return result;
}
#endif // GTEST_HAS_CLONE

// Spawns a child process with the same executable as the current process in
// a thread-safe manner and instructs it to run the death test.  The
// implementation uses fork(2) + exec.  On systems where clone(2) is
// available, it is used instead, being slightly more thread-safe.  On QNX,
// fork supports only single-threaded environments, so this function uses
// spawn(2) there instead.  The function dies with an error message if
// anything goes wrong.
static pid_t ExecDeathTestSpawnChild(char *const *argv, int close_fd)
{
    ExecDeathTestArgs args = {argv, close_fd};
    pid_t child_pid = -1;

#if GTEST_OS_QNX
    // Obtains the current directory and sets it to be closed in the child
    // process.
    const int cwd_fd = open(".", O_RDONLY);
    GTEST_DEATH_TEST_CHECK_(cwd_fd != -1);
    GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(cwd_fd, F_SETFD, FD_CLOEXEC));
    // We need to execute the test program in the same environment where
    // it was originally invoked.  Therefore we change to the original
    // working directory first.
    const char *const original_dir =
        UnitTest::GetInstance()->original_working_dir();
    // We can safely call chdir() as it's a direct system call.
    if (chdir(original_dir) != 0) {
        DeathTestAbort(std::string("chdir(\"") + original_dir + "\") failed: " + GetLastErrnoDescription());
        return EXIT_FAILURE;
    }

    int fd_flags;
    // Set close_fd to be closed after spawn.
    GTEST_DEATH_TEST_CHECK_SYSCALL_(fd_flags = fcntl(close_fd, F_GETFD));
    GTEST_DEATH_TEST_CHECK_SYSCALL_(fcntl(close_fd, F_SETFD,
                                          fd_flags | FD_CLOEXEC));
    struct inheritance inherit = {0};
    // spawn is a system call.
    child_pid = spawn(args.argv[0], 0, NULL, &inherit, args.argv, GetEnviron());
    // Restores the current working directory.
    GTEST_DEATH_TEST_CHECK_(fchdir(cwd_fd) != -1);
    GTEST_DEATH_TEST_CHECK_SYSCALL_(close(cwd_fd));

#else // GTEST_OS_QNX
#if GTEST_OS_LINUX
    // When a SIGPROF signal is received while fork() or clone() are executing,
    // the process may hang. To avoid this, we ignore SIGPROF here and re-enable
    // it after the call to fork()/clone() is complete.
    struct sigaction saved_sigprof_action;
    struct sigaction ignore_sigprof_action;
    memset(&ignore_sigprof_action, 0, sizeof(ignore_sigprof_action));
    sigemptyset(&ignore_sigprof_action.sa_mask);
    ignore_sigprof_action.sa_handler = SIG_IGN;
    GTEST_DEATH_TEST_CHECK_SYSCALL_(sigaction(
        SIGPROF, &ignore_sigprof_action, &saved_sigprof_action));
#endif // GTEST_OS_LINUX

#if GTEST_HAS_CLONE
    const bool use_fork = GTEST_FLAG(death_test_use_fork);

    if (!use_fork) {
        static const bool stack_grows_down = StackGrowsDown();
        const size_t stack_size = getpagesize();
        // MMAP_ANONYMOUS is not defined on Mac, so we use MAP_ANON instead.
        void *const stack = mmap(NULL, stack_size, PROT_READ | PROT_WRITE,
                                 MAP_ANON | MAP_PRIVATE, -1, 0);
        GTEST_DEATH_TEST_CHECK_(stack != MAP_FAILED);

        // Maximum stack alignment in bytes:  For a downward-growing stack, this
        // amount is subtracted from size of the stack space to get an address
        // that is within the stack space and is aligned on all systems we care
        // about.  As far as I know there is no ABI with stack alignment greater
        // than 64.  We assume stack and stack_size already have alignment of
        // kMaxStackAlignment.
        const size_t kMaxStackAlignment = 64;
        void *const stack_top =
            static_cast<char *>(stack) + (stack_grows_down ? stack_size - kMaxStackAlignment : 0);
        GTEST_DEATH_TEST_CHECK_(stack_size > kMaxStackAlignment && reinterpret_cast<intptr_t>(stack_top) % kMaxStackAlignment == 0);

        child_pid = clone(&ExecDeathTestChildMain, stack_top, SIGCHLD, &args);

        GTEST_DEATH_TEST_CHECK_(munmap(stack, stack_size) != -1);
    }
#else
    const bool use_fork = true;
#endif // GTEST_HAS_CLONE

    if (use_fork && (child_pid = fork()) == 0) {
        ExecDeathTestChildMain(&args);
        _exit(0);
    }
#endif // GTEST_OS_QNX
#if GTEST_OS_LINUX
    GTEST_DEATH_TEST_CHECK_SYSCALL_(
        sigaction(SIGPROF, &saved_sigprof_action, NULL));
#endif // GTEST_OS_LINUX

    GTEST_DEATH_TEST_CHECK_(child_pid != -1);
    return child_pid;
}

// The AssumeRole process for a fork-and-exec death test.  It re-executes the
// main program from the beginning, setting the --gtest_filter
// and --gtest_internal_run_death_test flags to cause only the current
// death test to be re-run.
DeathTest::TestRole ExecDeathTest::AssumeRole()
{
    const UnitTestImpl *const impl = GetUnitTestImpl();
    const InternalRunDeathTestFlag *const flag =
        impl->internal_run_death_test_flag();
    const TestInfo *const info = impl->current_test_info();
    const int death_test_index = info->result()->death_test_count();

    if (flag != NULL) {
        set_write_fd(flag->write_fd());
        return EXECUTE_TEST;
    }

    int pipe_fd[2];
    GTEST_DEATH_TEST_CHECK_(pipe(pipe_fd) != -1);
    // Clear the close-on-exec flag on the write end of the pipe, lest
    // it be closed when the child process does an exec:
    GTEST_DEATH_TEST_CHECK_(fcntl(pipe_fd[1], F_SETFD, 0) != -1);

    const std::string filter_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kFilterFlag + "="
        + info->test_case_name() + "." + info->name();
    const std::string internal_flag =
        std::string("--") + GTEST_FLAG_PREFIX_ + kInternalRunDeathTestFlag + "="
        + file_ + "|" + StreamableToString(line_) + "|"
        + StreamableToString(death_test_index) + "|"
        + StreamableToString(pipe_fd[1]);
    Arguments args;
    args.AddArguments(GetArgvsForDeathTestChildProcess());
    args.AddArgument(filter_flag.c_str());
    args.AddArgument(internal_flag.c_str());

    DeathTest::set_last_death_test_message("");

    CaptureStderr();
    // See the comment in NoExecDeathTest::AssumeRole for why the next line
    // is necessary.
    FlushInfoLog();

    const pid_t child_pid = ExecDeathTestSpawnChild(args.Argv(), pipe_fd[0]);
    GTEST_DEATH_TEST_CHECK_SYSCALL_(close(pipe_fd[1]));
    set_child_pid(child_pid);
    set_read_fd(pipe_fd[0]);
    set_spawned(true);
    return OVERSEE_TEST;
}

#endif // !GTEST_OS_WINDOWS

// Creates a concrete DeathTest-derived class that depends on the
// --gtest_death_test_style flag, and sets the pointer pointed to
// by the "test" argument to its address.  If the test should be
// skipped, sets that pointer to NULL.  Returns true, unless the
// flag is set to an invalid value.
bool DefaultDeathTestFactory::Create(const char *statement, const RE *regex,
                                     const char *file, int line,
                                     DeathTest **test)
{
    UnitTestImpl *const impl = GetUnitTestImpl();
    const InternalRunDeathTestFlag *const flag =
        impl->internal_run_death_test_flag();
    const int death_test_index = impl->current_test_info()
                                     ->increment_death_test_count();

    if (flag != NULL) {
        if (death_test_index > flag->index()) {
            DeathTest::set_last_death_test_message(
                "Death test count (" + StreamableToString(death_test_index)
                + ") somehow exceeded expected maximum ("
                + StreamableToString(flag->index()) + ")");
            return false;
        }

        if (!(flag->file() == file && flag->line() == line && flag->index() == death_test_index)) {
            *test = NULL;
            return true;
        }
    }

#if GTEST_OS_WINDOWS

    if (GTEST_FLAG(death_test_style) == "threadsafe" || GTEST_FLAG(death_test_style) == "fast") {
        *test = new WindowsDeathTest(statement, regex, file, line);
    }

#elif GTEST_OS_FUCHSIA

    if (GTEST_FLAG(death_test_style) == "threadsafe" || GTEST_FLAG(death_test_style) == "fast") {
        *test = new FuchsiaDeathTest(statement, regex, file, line);
    }

#else

    if (GTEST_FLAG(death_test_style) == "threadsafe") {
        *test = new ExecDeathTest(statement, regex, file, line);
    } else if (GTEST_FLAG(death_test_style) == "fast") {
        *test = new NoExecDeathTest(statement, regex);
    }

#endif // GTEST_OS_WINDOWS

    else { // NOLINT - this is more readable than unbalanced brackets inside #if.
        DeathTest::set_last_death_test_message(
            "Unknown death test style \"" + GTEST_FLAG(death_test_style)
            + "\" encountered");
        return false;
    }

    return true;
}

#if GTEST_OS_WINDOWS
// Recreates the pipe and event handles from the provided parameters,
// signals the event, and returns a file descriptor wrapped around the pipe
// handle. This function is called in the child process only.
static int GetStatusFileDescriptor(unsigned int parent_process_id,
                                   size_t write_handle_as_size_t,
                                   size_t event_handle_as_size_t)
{
    AutoHandle parent_process_handle(::OpenProcess(PROCESS_DUP_HANDLE,
                                                   FALSE, // Non-inheritable.
                                                   parent_process_id));
    if (parent_process_handle.Get() == INVALID_HANDLE_VALUE) {
        DeathTestAbort("Unable to open parent process " + StreamableToString(parent_process_id));
    }

    // FIXME: Replace the following check with a
    // compile-time assertion when available.
    GTEST_CHECK_(sizeof(HANDLE) <= sizeof(size_t));

    const HANDLE write_handle =
        reinterpret_cast<HANDLE>(write_handle_as_size_t);
    HANDLE dup_write_handle;

    // The newly initialized handle is accessible only in the parent
    // process. To obtain one accessible within the child, we need to use
    // DuplicateHandle.
    if (!::DuplicateHandle(parent_process_handle.Get(), write_handle,
                           ::GetCurrentProcess(), &dup_write_handle,
                           0x0, // Requested privileges ignored since
                           // DUPLICATE_SAME_ACCESS is used.
                           FALSE, // Request non-inheritable handler.
                           DUPLICATE_SAME_ACCESS)) {
        DeathTestAbort("Unable to duplicate the pipe handle " + StreamableToString(write_handle_as_size_t) + " from the parent process " + StreamableToString(parent_process_id));
    }

    const HANDLE event_handle = reinterpret_cast<HANDLE>(event_handle_as_size_t);
    HANDLE dup_event_handle;

    if (!::DuplicateHandle(parent_process_handle.Get(), event_handle,
                           ::GetCurrentProcess(), &dup_event_handle,
                           0x0,
                           FALSE,
                           DUPLICATE_SAME_ACCESS)) {
        DeathTestAbort("Unable to duplicate the event handle " + StreamableToString(event_handle_as_size_t) + " from the parent process " + StreamableToString(parent_process_id));
    }

    const int write_fd =
        ::_open_osfhandle(reinterpret_cast<intptr_t>(dup_write_handle), O_APPEND);
    if (write_fd == -1) {
        DeathTestAbort("Unable to convert pipe handle " + StreamableToString(write_handle_as_size_t) + " to a file descriptor");
    }

    // Signals the parent that the write end of the pipe has been acquired
    // so the parent can release its own write end.
    ::SetEvent(dup_event_handle);

    return write_fd;
}
#endif // GTEST_OS_WINDOWS

// Returns a newly created InternalRunDeathTestFlag object with fields
// initialized from the GTEST_FLAG(internal_run_death_test) flag if
// the flag is specified; otherwise returns NULL.
InternalRunDeathTestFlag *ParseInternalRunDeathTestFlag()
{
    if (GTEST_FLAG(internal_run_death_test) == "")
        return NULL;

    // GTEST_HAS_DEATH_TEST implies that we have ::std::string, so we
    // can use it here.
    int line = -1;
    int index = -1;
    ::std::vector<::std::string> fields;
    SplitString(GTEST_FLAG(internal_run_death_test).c_str(), '|', &fields);
    int write_fd = -1;

#if GTEST_OS_WINDOWS

    unsigned int parent_process_id = 0;
    size_t write_handle_as_size_t = 0;
    size_t event_handle_as_size_t = 0;

    if (fields.size() != 6
        || !ParseNaturalNumber(fields[1], &line)
        || !ParseNaturalNumber(fields[2], &index)
        || !ParseNaturalNumber(fields[3], &parent_process_id)
        || !ParseNaturalNumber(fields[4], &write_handle_as_size_t)
        || !ParseNaturalNumber(fields[5], &event_handle_as_size_t)) {
        DeathTestAbort("Bad --gtest_internal_run_death_test flag: " + GTEST_FLAG(internal_run_death_test));
    }
    write_fd = GetStatusFileDescriptor(parent_process_id,
                                       write_handle_as_size_t,
                                       event_handle_as_size_t);

#elif GTEST_OS_FUCHSIA

    if (fields.size() != 3
        || !ParseNaturalNumber(fields[1], &line)
        || !ParseNaturalNumber(fields[2], &index)) {
        DeathTestAbort("Bad --gtest_internal_run_death_test flag: "
                       + GTEST_FLAG(internal_run_death_test));
    }

#else

    if (fields.size() != 4
        || !ParseNaturalNumber(fields[1], &line)
        || !ParseNaturalNumber(fields[2], &index)
        || !ParseNaturalNumber(fields[3], &write_fd)) {
        DeathTestAbort("Bad --gtest_internal_run_death_test flag: "
                       + GTEST_FLAG(internal_run_death_test));
    }

#endif // GTEST_OS_WINDOWS

    return new InternalRunDeathTestFlag(fields[0], line, index, write_fd);
}

} // namespace internal

#endif // GTEST_HAS_DEATH_TEST

} // namespace testing
